I have the Clarion XMD-3 head unit in my boat and a Clarion 10 inch sub in front of the driver's feet. The amp is a Boss C800 with 150 watts RMS per channel and the amp is run bridged for 300 Watts total - which should be adequate for this sub as that is near its max.

The stupid question of the day is this: The unit has a crossover that can automatically filter out the high pass down to either 60, 90, or 120 HZ. It can also be set on REAR to get full output. When I put it on any of the low frequencies, I get hardly any sound out of my sub. If I put it on REAR and then use the amp to adjust my crossover, it sounds like what I expect. What is the purpose of this feature and why does it seem to be so useless? Is it just part of having a cheap sub?

The adjustment is probably set low (the default is right in the middle). Check the owner's manual, you can adjust that level up much more. Can't be done through the remote, must be done at the head unit.